In past proposals for systems which carried out both these processes gases have passed completely through a regenerative preheater, either one with rotating regenerative mass and static delivery ducts (German Federal Pat. Nos. 1,244,326 and 1,271,296) or with a static mass and rotating delivery hoods, and gas treatments such as scrubbing etc. have been carried out in a separate part of the apparatus to which the regenerator was connected by ducts.
The sealing arrangements between ducts on the one hand, and the regenerative mass on the other hand of the regenerative preheater presents considerable difficulties and it has always been necessary to achieve this sealing at both of the end faces of the regenerative mass. Because of the necessity for accuracy and wear resistance at these sealing surfaces and because of the need for structural strength the support structure for the regenerative mass has always to have been made entirely of steel at these areas, and this is a material of limited resistance to corrosion and heat in the high temperature and/or corrosive conditions which are liable to be met in the working of the apparatus.